Numerous proposals have been made regarding a fluidized bed catalyst for producing acrylonitrile by vapor phase ammoxidation of propylene by molecular oxygen and ammonia. For example, fluidized bed catalysts containing molybdenum have been disclosed having as main components thereof molybdenum, bismuth and iron, and which are further compounded with various metal components (Patent Documents 1 to 10).
In addition, a process for regenerating a catalyst of low activity by adding molybdenum-containing substances to a catalyst layer during ammoxidation reaction (hereinafter, simply referred to as a reaction) in a process for producing acrylonitrile by vapor phase ammoxidation with a catalyst including molybdenum; and a process to maintain the performance of a catalyst for a long time by adding molybdenum-containing substances in addition to a catalyst including molybdenum in the catalyst before the start of the reaction have been proposed (Patent Documents 11 to 15).
However, molybdenum vaporizes from a catalyst and molybdenum-containing substances, and is deposited on cooling instruments such as a cooling coil of the fluidized bed reactor in a process to regenerate a catalyst of low activity by adding molybdenum-containing substances to the catalyst during ammoxidation in a conventional process for producing acrylonitrile by vapor phase ammoxidation with a catalyst including molybdenum, and in a process to maintain the performance of a catalyst for a long time by adding molybdenum-containing substances in addition to a catalyst including molybdenum in the catalyst before the start of the reaction. If the molybdenum is deposited on cooling instruments, there are cases in which it becomes difficult to stably operate the fluidized bed reactor for a long time due to heat transfer inhibition.
Therefore, in order to stably produce acrylonitrile for a long time, it is desirable to reduce the amount of molybdenum-containing substances added, and in order to accomplish this, it is desirable to develop a catalyst for producing acrylonitrile capable of maintaining stable yield of acrylonitrile for a long time using as small an added amount of molybdenum-containing substances as possible.
In addition, a fluidized bed reactor can be stably operated with conventional catalysts for a long time without such problems described above. However, these catalysts are not industrially suitable due to low yield production of acrylonitrile. Therefore, development of a catalyst for producing acrylonitrile stably for a long time and also at high yield has been desired.
[Patent Document 1] U.S. Pat. No. 5,212,137
[Patent Document 2] U.S. Pat. No. 5,688,739
[Patent Document 3] U.S. Pat. No. 5,834,394
[Patent Document 4] Japanese Patent No. 3214975
[Patent Document 5] Japanese Patent No. 3534431
[Patent Document 6] US Patent Application No. 2004/0106817
[Patent Document 7] Japanese Unexamined Patent Application, First Publication No. Hei 10-043595
[Patent Document 8] Japanese Laid-Open Patent Application No. 2001-114740
[Patent Document 9] Japanese Laid-Open Patent Application No. 2001-187771
[Patent Document 10] Japanese Laid-Open Patent Application No. 2003-117397
[Patent Document 11] Japanese Examined Patent Application, Second Publication No. Sho 58-57422
[Patent Document 12] Japanese Unexamined Patent Application, First Publication No. Sho 59-193136
[Patent Document 13] German Patent Application No. 3311521
[Patent Document 14] Japanese Examined Patent Application, Second Publication No. Hei 2-56938
[Patent Document 15] International Publication WO No. 97/33863 pamphlet